The present invention relates to apparatus for removing dust from intake air for an internal combustion engine.
Japanese Utility Model Examined Publication No. 50126/81 shows an example of a full cyclone type air cleaner including an annular swirl chamber. During a swirl motion of the intake air in the swirl chamber, dust entrained in the air is discharged through a passage at the perimeter of the swirl chamber by a cyclone effect.
However, a conventional full cyclone type air cleaner must have a large swirl chamber to provide an air passage extending to a filter downstream of the swirl chamber. This makes the passage structure unduly large and complicated. Therefore, a conventional cyclone air cleaner suffers from disadvantages in that intake air passage flow resistance is increased, and the complicated overall structure would require high costs. Also, the opening for the dust discharge must be large so intake noise is reduced. Furthermore, it would be impossible to discharge the dust retained at corner portions of the air passage.